Self-toning photographic paper.



UNITED STATES PATENT OFFICE.

CARL SOFUS POULSEN, OF VALBY, NEAR COPENHAGEN, DENMARK.

SE-LF-TONING PHOTOGRAPHIC PAPER.

Specification of Letters Patent.

Patented Nov. 20, 1906.

Application filed October 1'7, 1905. Serial No. 288,170.

of Denmark, have invented new and useful Improvements in Self-Toning Photographic Paper, of which the following is a 'specifica tion.

None of the gold-containing compositions heretofore proposed for the production of self-toning paper have satisfactorily solved the problem of being able to dispense with the gold-bath and of producing a genuine permanent gold tone, while also supplying a durable and readily-available paper. When the gold is used in the form of oXid, nitrate, sulfate, rhodanid, or, as is most generally the case, in the-form of chlorid (c. f., the specifications of British Letters Patent No. 6,651 of 1896, No. 15,352 of 1896, and No. 6,609 of 1901, and German Patent specifications Nos. 67,016, 77,162, 110,089, and 132,421) the composition is either not sufliciently durable when the paper is kept, or it acts too slowly in the water-b ath, or the reaction (the toning) does not proceed as it ought to. Even when a real gold-tone is produced in some cases it is so weak that it is apt to disappear wholly or in part during the burnishing operation.

Now the object of this invention is to provide a self-toning paper which is not only durable and gives a genuine durable gold tone on dipping into a salt-water or like bath, but has also the special property that the gold tone is independent of the duration of the bath and is determined only by the concentration or composition of the bath, so that with a given property of the bath a definite tone will always be obtained without fail which is instantly formed and does not alter even when the paper remains for a long time in the bath. This result is obtained by introducing the gold salt along with a dyestuffsuch as methyl violet, fuchsin, or the likeinto an emulsion containing silver, in which the silver is partly combined with cyanogen or sulfocyanogen.

Accordingly to the silver-containing emulsion (collodium, gelatin, albumen, or the like) used in the production of photographic paper there is added a dyestufl' of the kind referred to, for instance, in the proportion .of five to fifteen milligrams to one thousand grams emulsion, and alkali cyanid or sulfocyanid, for instance, in the proportion of three to six grams, as also gold chlorid or the like in such proportionfor instance, two to three gramsth at the gold is present in sufficient degree of concentration in the emulsion which is used for the sensitized films of the self-toning paper.

The toningt. e., the reaction in the water or salt bath or like bath-proceeds, as above mentioned, with the employment of the improved paper in a surprisingly short time and with absolute security.

According to the proportion of salt in the bath the tone can be varied with exactitude from red-brown to the most extreme blueblack.

There is no risk and no special attention required in the toning operation.

Having now particularly described and ascertained the nature of my said invention and in what manner the same is to be performed, I declare that what I claim is 1. A self-toning photographic paper, coated with a sensitized film, containing a silver salt, a gold salt and a dyestuff.'

2. A self-toning photographic paper, coated with a sensitized film, formed of an emulsion containing a silver salt, which is partly combined with cyanogen, a gold salt and a dyestuif.

In testimony whereof I have signed my name to this specification in the presence of two subscribing witnesses.

CARL SOFUS POULSEN.

Witnesses:

ERNEST BOUTARD, ALBERT G. MIcHELsoN. 

